The present invention relates to hoisting apparatus and more particularly to an improved hoist drum or spool for receiving wire rope and the like and which prevents crushing and undue wear of the wire rope.
Conventional hoist drums are shown for example in the LeBus patents, U.S. Pat. No. 3,150,844, issued Sept. 29, 1964, and in U.S. Pat. No. 3,391,879, issued July 9, 1968. Such hoist drums generally include a cylindrical drum and flanges at each end and are intended to support at least several layers of evenly wound wire rope. The wire rope is wound around the drums and progresses in a circumferential and longitudinal path from one end of the drum to the other end to form discrete layers. The first layer of the wire rope on the drum extends from the inner face of one drum flange member to the inner face of a drum flange member at the opposite end of the drum. As the wire rope reaches the other flange, it forms a second layer having a reverse helical wrap and the coils of the second layer lie in the grooves formed by the coils of the first layer. Each succeeding layer of wire rope is reversed in a similar manner to provide for the winding of the wire rope on the spool. During the spooling process of each layer, as the wire rope is being wound and approaches one of the flanges, the gap or space between an adjacent coil of the wire rope and the flange eventually becomes less than the thickness of the wire rope. The wire rope is thus pinched therebetween and this pinching effect forces the wire rope outwardly wherein continued winding causes the wire rope to form a new layer whereupon the wire rope can begin to traverse the length of the drum in the opposite direction toward the other flange.
Due to the pinching action of the wire rope adjacent to the drum flange, that portion of the wire rope being pinched is subjected to both crushing and scrubbing action and to greater wear than the remainder of the rope. This problem is increased in the event that the hoist drum is used such that that portion of the rope subjected to pinching is played out and then rewound frequently, thus causing increased crushing, scrubbing, and wear of a localized portion of the rope. The pinching effect referred to above also has the undesirable effect of subjecting the drum flange to localized wear forces frequently causing premature wear or distortion of the drum flanges and costly maintenance or replacement.